The present invention relates generally to structures that prevent or retard electromagnetic interference (“EMI”) emissions from connector assemblies, and more particularly to an EMI shroud intended for use on a metal shielding cage for blocking electromagnetic interference emissions.
It is a common practice in the electronic arts to connect cables to a circuit board by utilizing plug connectors at the ends of the cables which are intended for insertion into an opposing mating connector. The mating connector is typically mounted on a circuit board, which is held within an exterior housing. Such an arrangement is typically found in servers and routers. These devices have multiple connector assemblies that now operate at high speeds, typically 2 gigabits per second and greater. The high speed electrical transmission in these devices can produce electromagnetic emissions, which may leak from the connection between the plug connector and its mating connector. These emissions can cause problems in high speed transmissions in that they can negatively influence signal transmissions between the connectors.
These types of transmissions are routinely reduced by the use of a metal shielding cage that is also mounted to the circuit board and which surrounds the mating connector in the device. These cages have openings that open to a faceplate, which is commonly referred to as a bezel in the art. These openings define an entrance leading toward the mating connector into which the plug connector is inserted. Testing has determined that despite the metal shielding cages, EMI leakage still occurs in such structure, primarily at the areas where the shielding cages meet the circuit board and around the opening(s) of the faceplate or bezel, into which the cage openings extend. Conductive gaskets have been developed in efforts to address this problem.
Problems still exist in the use of gaskets, for it is desired that the gaskets be conductive and held in close contact to both the shielding cages and the faceplate. These cages are becoming smaller and smaller in size as the overall size of most electronic devices continues to diminish. The small size of the cages often makes it difficult to develop a structure that will force the EMI gasket into reliable contact with the faceplate and the cage, without detrimentally affecting the strength of the shielding cage.
Accordingly, the present invention is directed to an improved EMI gasket structure that takes the form of a shroud and which overcomes disadvantages of the prior art. An important problem to be addressed is how to enhance EMI-preventing contact between components of connector assemblies.
Examples of prior approaches proposed for addressing EMI shielding problems include U.S. Pat. No. 5,204,496 (Boulay, et al.) and U.S. Pat. No. 6,420,009 (Cheng) that show incorporating a bent flange EMI gasket. U.S. Pat. No. 6,851,978 (Akama, et al) proposes a hook for a shielding cage gasket. Included in U.S. Pat. No. 6,752,663 (Bright, et al) is a shielding gasket assembly having pre-formed slots that fit over and receive mounting feet of the bottom of a cage. The combination of a formed gasket and a backing plate is shown in U.S. Pat. No. 6,878,872 (Lloyd, et al.). These patents, and all other references noted herein, are hereby incorporated hereinto by reference.